Description Usage Arguments Details Value Examples

View source: R/get_adjacencies.R

Fast calculation of adjacencies between classes in a raster

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 | ```
get_adjacencies(landscape, neighbourhood, what, upper)
## S3 method for class 'RasterLayer'
get_adjacencies(landscape, neighbourhood = 4, what = "full", upper = FALSE)
## S3 method for class 'RasterStack'
get_adjacencies(landscape, neighbourhood = 4, what = "full", upper = FALSE)
## S3 method for class 'RasterBrick'
get_adjacencies(landscape, neighbourhood = 4, what = "full", upper = FALSE)
## S3 method for class 'stars'
get_adjacencies(landscape, neighbourhood = 4, what = "full", upper = FALSE)
## S3 method for class 'list'
get_adjacencies(landscape, neighbourhood = 4, what = "full", upper = FALSE)
## S3 method for class 'matrix'
get_adjacencies(landscape, neighbourhood = 4, what = "full", upper = FALSE)
``` |

`landscape` |
Raster* Layer, Stack, Brick, SpatRaster (terra), stars, or a list of rasterLayers. |

`neighbourhood` |
The number of directions in which cell adjacencies are considered as neighbours: 4 (rook's case), 8 (queen's case) or a binary matrix where the ones define the neighbourhood. The default is 4. |

`what` |
Which adjacencies to calculate: "full" for a full adjacency matrix, "like" for the diagonal, "unlike" for the off diagonal part of the matrix and "triangle" for a triangular matrix counting adjacencies only once. |

`upper` |
Logical value indicating whether the upper triangle of the adjacency matrix should be returned (default FALSE). |

A fast implementation with Rcpp to calculate the adjacency matrix for raster. The adjacency matrix is most often used in landscape metrics to describe the configuration of landscapes, is it is a cellwise count of edges between classes.

The "full" adjacency matrix is double-count method, as it contains the pairwise counts of cells between all classes. The diagonal of this matrix contains the like adjacencies, a count for how many edges a shared in each class with the same class.

The "unlike" adjacencies are counting the cellwise edges between different classes.

matrix with adjacencies between classes in a raster and between cells from the same class.

1 2 3 4 5 6 7 8 9 10 11 12 | ```
# calculate full adjacency matrix
get_adjacencies(landscape, 4)
# count diagonal neighbour adjacencies
diagonal_matrix <- matrix(c(1, NA, 1,
NA, 0, NA,
1, NA, 1), 3, 3, byrow = TRUE)
get_adjacencies(landscape, diagonal_matrix)
# equivalent with the raster package:
adjacencies <- raster::adjacent(landscape, 1:raster::ncell(landscape), 4, pairs=TRUE)
table(landscape[adjacencies[,1]], landscape[adjacencies[,2]])
``` |

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